1. Field of the Invention
The present invention relates to an under seal device of a linear movement guide bearing used in machine tools, industrial machines, and the like.
2. Description of the Relevant Art
A prior art under seal device of a linear movement guide bearing is disclosed, for example, in Japanese Utility Model Laid-Open Publication Hei No. 1-178221. This linear movement guide bearing includes a guide rail extending in an axial direction and having ball rolling grooves respectively formed in both side surfaces, a slider main body fitted on the guide rail for movement in an axial direction and having ball rolling grooves respectively formed in inner surfaces of both side walls so that the ball rolling grooves of the slider respectively correspond to the ball rolling grooves of the guide rail, the slider main body further having through bores as ball return paths respectively formed in both of the side walls in parallel with the ball rolling grooves of the slider main body, end caps respectively joined to axial opposite ends of the slider main body, each of the end caps having a pair of semicircular-shaped curved paths each communicating a corresponding one of the ball rolling grooves with a corresponding one of the through bores, and a plurality of balls loaded in opposing ball rolling grooves of the guide rail and the slider main body, the ball return paths, and the curved paths.
In this linear movement guide bearing, each of the end caps has seal holding grooves formed in an end surface which is joined with the slider main body for holding end portions of a pair of under seals which are inserted therein. Further, the slider main body has recessed under seal accommodating portions respectively formed in the lower surfaces of both of the side walls.
On the other hand, each of the under seals includes a mandrel which abuts against the under seal accommodating portion and a rubber body bonded to the mandrel and having a lip portion extending from an outer edge of the mandrel to slidably contact a side surface of the guide rail. The rubber body further has elastic projections protruding from longitudinal opposite ends of the rubber body.
In mounting the under seal, the under seal is applied to the under seal accommodating portion of the slider main body and the opposite ends of the under seal are respectively fitted into the under seal holding grooves formed in the joining surface of the end caps with the slider main body. As a result, the elastic projections protruding from the opposite ends of the under seal are pressed against the groove surfaces of the seal holding grooves to hold the under seal in place by an elastic force. Thus, the under seal can be fixed in position by substantially a single mounting operation.
However, in such a prior art under seal device of a linear movement guide bearing, the fixing of the under seal is primarily aimed at preventing the fall off of the under seal from the slider. Thus, the wear of the under seal is not especially taken into consideration and a problem is encountered in that the sealing performance of the under seal deteriorates due to use over a long period of time.
Furthermore, in the prior art under seal of the groove fitting type, since a cut groove is formed in the end cap which is made of a synthetic resin, in the case of small-type linear movement guide bearings, there is a problem in that the thickness of the end cap for holding the under seal becomes too thin and a crack can occur in the end cap.
Furthermore, since the sealing between the under seal and side seals which are attached to outer sides of the end caps is not entirely taken into consideration, a problem develops in that the sealing performance in these portions is not sufficient.